Restraint systems are used to reduce injuries to drivers and passengers in all types of vehicles. The design of a restraint system depends upon the vehicle the restraint system is used in and the expected use of the vehicle. Restraint systems used in off road vehicles and race cars are very well developed. Drivers of race cars involved in high speed crashes frequently walk away from the vehicle following a crash or escape with relatively minor injuries due to protection provided by the driver cage and the restraint system which holds the driver in a safe area defined by the driver cage.
The primary functions of restraint systems are to hold the driver or passenger within a safe area in the vehicle, to hold the driver in a position from which he can operate the vehicle controls, and to reduce injury to drivers and passengers. Restraint systems are currently available which hold a person within a safe area inside a vehicle. Some restraint systems that are currently available allow a person to move to positions from which it is difficult to operate vehicle controls. It is also known for current systems to cause some injury to the person restrained.
Restraint systems normally include straps made from nylon or other suitable material. When these straps are placed under a load they tend to straighten and become hard. The pressure exerted on these straps by a human body during a crash can be sufficient to break bones. Shoulder straps can break collar bones, for example. After the collar bone breaks, the sternum may hyperextend and the upper body may force the shoulder straps apart and move between the shoulder straps.
The lap belt portion of a restraint system can also cause injury to the person being restrained. If a lap belt is too low, the hip joints can be injured. If a lap belt is too high, the abdomen may be injured. To prevent these injuries, the lap belt should restrain the pelvis and the pelvis should not slide out of the lap belt in either direction.
During a sudden deceleration, a person tends to submarine, or slide down and through the lap belt portion of a restraint system. When a person submarines, the lap belt moves up above the pelvis and into contact with the abdomen. The movement of the lap belt on the abdomen toward the thorax tends to move organs in the abdomen toward and into the chest cavity thereby making breathing difficult or impossible.
Straps have been run from the lap belt down between the legs of a person being restrained, over the forward edge of a seat, and to an anchor point on the floor of the driver or passenger compartment. These straps limit submarining, but do not prevent the problem. Such straps generally allow a person to slide down and forward until the pelvis reaches the forward edge of the seat. Such movement may result in injury and will likely place the person in a position which makes it difficult or impossible to operate vehicle controls.
Fire is a possibility in any vehicle crash due to the presence of fuel for internal combustion engines. A body restraint system must, therefore, allow a quick exit from the restraint system. Even in a battery powered vehicle it may be necessary to make a quick exit following a collision due to the presence of chemicals in the batteries. Cam release assemblies have been used with restraint systems to allow quick exits. Some of the currently available release assemblies require frequent cleaning and lubrication to ensure that the release pins do not stick, making it difficult for a person to get out of the restraint system.
Pads in the form of sleeves have been provided that slide over the shoulder straps of a restraint system. The primary purpose of these pads is to prevent the shoulder straps from rubbing the shoulder or neck of a person being restrained. These sleeves frequently slide up or down on the shoulder straps to positions which allow contact between the shoulder strap and a person's shoulder and neck.